小编典典

如何在C#中拖动和移动形状

c#

在C#WindoeFormsApplication中,是否可以选择,从而用鼠标移动或删除绘制的形状?就像Windows的画图程序一样。

形状绘图工作得很好,所有点都存储在某个数组中。作为此线图示例

Point Latest { get; set; }

List<Point> _points = new List<Point>();

protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);

// Save the mouse coordinates
Latest = new Point(e.X, e.Y);

// Force to invalidate the form client area and immediately redraw itself. 
Refresh();
}

protected override void OnPaint(PaintEventArgs e)
{
var g = e.Graphics;
base.OnPaint(e);

if (_points.Count > 0)
{
    var pen = new Pen(Color.Navy);
    var pt = _points[0];
    for(var i=1; _points.Count > i; i++)
    {
        var next = _points[i];
        g.DrawLine(pen, pt, next);
        pt = next;
    }

    g.DrawLine(pen, pt, Latest);
}
}

private void Form1_MouseClick(object sender, MouseEventArgs e)
{
Latest = new Point(e.X, e.Y);
_points.Add(Latest);
Refresh();
}

我可以让它通过基本线性代数来计算鼠标位置和每条线之间的最短距离,并设置一个阈值距离,如果它比阈值短,请选中此线,并可以用鼠标拖动或编辑它。但是,只是想知道,对于这种任务,还有什么方法更易于管理吗?主要是选择部分。任何建议将不胜感激,谢谢!


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2020-05-19

共1个答案

小编典典

要达到测试形状,您不需要线性代数。您可以GraphicsPath为您的形状创建,然后使用GraphicsPath.IsVisibleGraphicsPath.IsOutlineVisible方法执行命中测试。

  • 要检查路径中是否有点,例如填充的形状,请使用IsVisible

  • 要测试线条,曲线或空的形状,可以使用IsOutlineVisible

例如,您可以创建一个基本IShape接口,其中包含用于命中测试,绘图和移动的方法。然后在类中实现这些方法。您还可以创建一个DrawingSurface控件,该控件可以处理命中测试,绘图和移动IShape对象。

在下面的示例中,我们创建IShape接口LineCircle类。我们也创建一个DrawingSurface控件。为了测试该示例,它足以将DrawingSurface控件放在a上Form并处理Load表单事件并添加一些形状,然后运行应用程序并尝试移动形状。

形状

该接口包含一些有用的方法,如果有任何类可以实现这些方法,则可以将它们用于绘图,命中测试和移动。在本示例的最后,您可以看到一个DrawingSurface可以IShape简单地与实现一起使用的控件:

public interface IShape
{
    GraphicsPath GetPath();
    bool HitTest(Point p);
    void Draw(Graphics g);
    void Move(Point d);
}

线

这是实现IShape接口的线类。在点击测试时,如果您单击行,则HitTest返回true。另外,为了让您更简单地选择行,我为命中测试添加了2分:

public class Line : IShape
{
    public Line() { LineWidth = 2; LineColor = Color.Black; }
    public int LineWidth { get; set; }
    public Color LineColor { get; set; }
    public Point Point1 { get; set; }
    public Point Point2 { get; set; }
    public GraphicsPath GetPath()
    {
        var path = new GraphicsPath();
        path.AddLine(Point1, Point2);
        return path;
    }
    public bool HitTest(Point p)
    {
        var result = false;
        using (var path = GetPath())
        using (var pen = new Pen(LineColor, LineWidth + 2))
            result = path.IsOutlineVisible(p, pen);
        return result;
    }
    public void Draw(Graphics g)
    {
        using (var path = GetPath())
        using (var pen = new Pen(LineColor, LineWidth))
            g.DrawPath(pen, path);
    }
    public void Move(Point d)
    {
        Point1 = new Point(Point1.X + d.X, Point1.Y + d.Y);
        Point2 = new Point(Point2.X + d.X, Point2.Y + d.Y);
    }
}

这是一个实现IShape接口的圈子类。如果您单击圆圈,则进行命中测试时,HitTest返回true:

public class Circle : IShape
{
    public Circle() { FillColor = Color.Black; }
    public Color FillColor { get; set; }
    public Point Center { get; set; }
    public int Radious { get; set; }
    public GraphicsPath GetPath()
    {
        var path = new GraphicsPath();
        var p = Center;
        p.Offset(-Radious, -Radious);
        path.AddEllipse(p.X, p.Y, 2 * Radious, 2 * Radious);
        return path;
    }

    public bool HitTest(Point p)
    {
        var result = false;
        using (var path = GetPath())
            result = path.IsVisible(p);
        return result;
    }
    public void Draw(Graphics g)
    {
        using (var path = GetPath())
        using (var brush = new SolidBrush(FillColor))
            g.FillPath(brush, path);
    }
    public void Move(Point d)
    {
        Center = new Point(Center.X + d.X, Center.Y + d.Y);
    }
}

图纸表面

该控件绘制形状列表。此外,它还会执行命中测试,MouseDown并在拖动时移动形状。您应该添加一些形状,例如Line或添加CircleShapes控件集合中。

public class DrawingSurface : Control
{
    public List<IShape> Shapes { get; private set; }
    IShape selectedShape;
    bool moving;
    Point previousPoint = Point.Empty;
    public DrawingSurface() { DoubleBuffered = true; Shapes = new List<IShape>(); }
    protected override void OnMouseDown(MouseEventArgs e)
    {
        for (var i = Shapes.Count - 1; i >= 0; i--)
            if (Shapes[i].HitTest(e.Location)) { selectedShape = Shapes[i]; break; }
        if (selectedShape != null) { moving = true; previousPoint = e.Location; }
        base.OnMouseDown(e);
    }
    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (moving) {
            var d = new Point(e.X - previousPoint.X, e.Y - previousPoint.Y);
            selectedShape.Move(d);
            previousPoint = e.Location;
            this.Invalidate();
        }
        base.OnMouseMove(e);
    }
    protected override void OnMouseUp(MouseEventArgs e)
    {
        if (moving) { selectedShape = null; moving = false; }
        base.OnMouseUp(e);
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
        foreach (var shape in Shapes)
            shape.Draw(e.Graphics);
    }
}
2020-05-19